A new study in mice suggests that a biological process known as cellular senescence, which can be induced by cancer treatments, may play a role in bone loss associated with chemotherapy and radiation. Senescence occurs when a cell permanently stops dividing but does not die. Senescent cells release a variety of substances into their environments that may affect neighboring cells. “Senescent cells release many molecules,” said Sheila Stewart, Ph.D., of the Washington University School of Medicine in St. Louis, who led the study. “We found that some of the molecules released by senescent cells drive bone loss in mice receiving chemotherapy.” Specifically, molecular signals from chemotherapy-induced senescent cells disrupted a process known as bone remodeling, the researchers reported in Cancer Research on January 23. During bone remodeling, cells called osteoclasts dismantle old bone and cells called osteoblasts build new bone. Normally, osteoblasts and osteoclasts work in concert. “But when the balance is disrupted [by signals from senescent cells], bone can become too thin,” said Dr. Stewart. Thinning bone can lead to osteoporosis, increasing the risk of fractures and bone pain. The researchers also showed that two investigational drugs could block molecular signals from senescent cells that disrupt bone remodeling in mice. This approach, the researchers noted, could be evaluated as a possible strategy for preventing chemotherapy-induced bone loss in patients.